Imine-Oxazoline (ImOx): A C1-Symmetric N,N-Bidentate Ligand for Asymmetric Catalysis

IF 11.3 1区化学 Q1 CHEMISTRY, PHYSICAL

ACS Catalysis Pub Date : 2025-06-17 DOI:10.1021/acscatal.5c03134

Elliot S. Silk, Haozhe Zhu, Alexander G. Shtukenberg, Tianning Diao

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Abstract

Asymmetric catalysis relies on the design of chiral ligands, but the variety of nitrogen-based ligands remains limited. To address this gap, we have developed a class of C₁-symmetric N,N-bidentate ligands, imine-oxazoline (ImOx), derived from amino acids through a four-step synthesis. ImOx features an imine moiety conjugated with a chiral oxazoline ring as a hybrid of α-diimine (ADI) and pyridine oxazoline (PyOx) ligands. Its low symmetry allows for independent optimization at both coordination sites. ImOx improves the enantioselectivity of palladium-catalyzed conjugate addition reactions, demonstrating a strong correlation between ee and the steric effects on both the imine and oxazoline sites. Studies on well-defined organopalladium intermediates reveal that the steric bulk of ImOx necessitates a cationic pathway to promote alkene insertion. Structural characterization of ImOx suggests a stronger trans-influence compared to PyOx. Moreover, ImOx demonstrates versatile redox activity, promoting the reduction of nickel complexes and stabilizing nickel radical complexes. We anticipate that ImOx will expand the toolkit of chiral N-ligands for asymmetric catalysis.

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亚胺-恶唑啉（ImOx）：用于不对称催化的c1对称N，N双齿配体

不对称催化依赖于手性配体的设计，但氮基配体的种类仍然有限。为了解决这一问题，我们开发了一类c1对称的N，N双齿配体，亚胺-恶唑啉（ImOx），通过四步合成从氨基酸中提取。ImOx是α-二亚胺（ADI）和吡啶恶唑啉（PyOx）配体的杂化体，其特征是亚胺部分与手性恶唑啉环共轭。它的低对称性允许在两个协调点进行独立的优化。ImOx提高了钯催化共轭加成反应的对映选择性，表明ee与亚胺和恶唑啉位点的空间效应之间存在很强的相关性。对定义明确的有机钯中间体的研究表明，ImOx的立体体积需要一个阳离子途径来促进烯烃的插入。ImOx的结构表征表明，与PyOx相比，ImOx的反式影响更强。此外，ImOx具有多种氧化还原活性，促进镍配合物的还原和稳定镍自由基配合物。我们预计ImOx将扩大用于不对称催化的手性n配体的工具箱。

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来源期刊

ACS Catalysis CHEMISTRY, PHYSICAL-

CiteScore

20.80

自引率

6.20%

发文量

1253

审稿时长

1.5 months

期刊介绍： ACS Catalysis is an esteemed journal that publishes original research in the fields of heterogeneous catalysis, molecular catalysis, and biocatalysis. It offers broad coverage across diverse areas such as life sciences, organometallics and synthesis, photochemistry and electrochemistry, drug discovery and synthesis, materials science, environmental protection, polymer discovery and synthesis, and energy and fuels. The scope of the journal is to showcase innovative work in various aspects of catalysis. This includes new reactions and novel synthetic approaches utilizing known catalysts, the discovery or modification of new catalysts, elucidation of catalytic mechanisms through cutting-edge investigations, practical enhancements of existing processes, as well as conceptual advances in the field. Contributions to ACS Catalysis can encompass both experimental and theoretical research focused on catalytic molecules, macromolecules, and materials that exhibit catalytic turnover.